<html>
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	<form action="">
		<p>
			用户名:
			<input type="text" id="demo">
			<label for="demo">点击填写用户名</label>
		</p>
	</form>
</body>
</html>